Method and apparatus for molding an elongated hollow article

Abstract

A molding apparatus includes a mold comprising a stationary outer mold with a substantially tubular mold cavity, a moveable end mold with an end mold cavity alignable with the tubular mold cavity, and a stationary elongated mold core with a fluid channel therethrough, the mold core extending through the tubular cavity into the end mold cavity. A method of using the apparatus includes injecting a molding material at a material flow rate into the mold, moving the end mold at a speed in a linear direction from a first position to a second position, supplying a fluid at a fluid flow rate to the fluid channel, and varying at least one of the material flow rate, the end mold speed and the fluid flow rate as the end mold moves from the first position to the second position.

What is claimed is: 
     
       1. A method of injection molding of an elongated hollow article, said method comprising the steps of:
 injecting a molding material at a material flow rate into a mold comprising a stationary outer mold with a substantially tubular mold cavity, a moveable end mold with an end mold cavity aligned with the tubular mold cavity, and a stationary elongated mold core with a fluid channel therethrough, the mold core extending through the tubular cavity into the end mold cavity; 
 moving the end mold at a speed in a linear direction from a first position with the end mold cavity aligned with the central mold cavity to a second position at a predetermined distance between the end mold and the outer mold; 
 supplying a fluid at a fluid flow rate to the fluid channel in the elongated mold core; and 
 varying selectively, via one or more controllers, at least one of the material flow rate, the end mold speed and the fluid flow rate at one or more points as the end mold moves between the first position and the second position, the one or more controllers configured to control one or more of a metering device configured to inject the molding material, an actuator configured to move the end mold, and a valve configured to supply the fluid to vary selectively the at least one of the material flow rate, the end mold speed, and the fluid flow rate at the one of more points as the end mold moves between the first position and the second position. 
 
     
     
       2. The method according to  claim 1 , wherein the varying step comprises balancing the material flow rate, the end mold speed and the fluid flow rate. 
     
     
       3. The method according to  claim 1 , wherein the varying step comprises increasing the material flow rate after the end mold begins moving, and decreasing subsequently the material flow rate before the end mold reaches the second position. 
     
     
       4. The method according to  claim 3 , wherein the varying step comprises increasing the material flow rate immediately after the end mold begins moving, and decreasing subsequently the material flow rate before the end mold reaches the second position. 
     
     
       5. The method according to  claim 1 , wherein the varying step comprises progressively increasing the end mold speed as the end mold moves between the first position and the second position. 
     
     
       6. The method according to  claim 5 , wherein the varying step comprises progressively increasing the end mold speed as the end mold moves between the first position and a third position between the first and second positions, and substantially increasing the end mold speed as the end mold moves between the third and second positions. 
     
     
       7. The method according to  claim 1 , wherein the supplying step occurs simultaneously with the moving step. 
     
     
       8. The method according to  claim 1 , wherein the supplying step is delayed relative to the moving step. 
     
     
       9. The method according to  claim 1 , wherein the varying step comprises increasing the fluid flow rate immediately before the end mold reaches the second position.